Setting specific FPS for video
As you have noticed the FPS can only be set to integer values. To get a fractional frame rate you need to also set the framerate base which you can find right under the FPS.

The easy way to get the right base value is to enter a calculation which is the set fps divided by the target rate. eg 30 / 29.75, when you then press enter it will show the value of 1.008 and the frame rate will show as Custom (29.75 fps)